1. Field of the Invention
This invention relates to a picture transmission system used in a picture remote surveillance system or a visual telephone, etc.
2. Description of the Related Art
Moving pictures have compression efficiency higher than still pictures, and can be advantageously transmitted at a low transmission rate. As a moving picture transmission system as mentioned above, systems based on the H.261 standard of CCITT (Comite Consultatif International Telegraphique et Telephonique) are generally used. On the other hand, as a transmission system for still picture, there are systems having transmission efficiency caused to be improved by the picture compression/decompression technology in conformity with the JPEG (Joint Photographic Coding Experts Group) standard or corresponding thereto.
In the case of a moving picture transmitted at a low transmission rate, moving pictures of natural motion (movement) can be obtained on real time basis, but the picture quality disadvantageously becomes lower. For example in the case where surveillance at a remote place is carried out by such moving picture, there was the problem that even if an extraordinary state takes place and an operator notices the of picture on the screen, the image is unclear or obscure to such a degree that the operator cannot discriminate the detailed portions, thus failing to obtain detailed information.
On the contrary, in the case of a transmission of still picture, higher picture quality can be obtained as compared to that of a moving picture, a but the compression efficiency is lower and it takes much time in transmission. For this reason, motion was discontinuous so that the picture becomes difficult to see and there was the possibility that operator may overlook important information.